Polymerizable amphiphilic molecules and hydrolysable alkyl silanes are employed to form thin films on various surfaces. Thin films have numerous and diverse useful purposes. For example, a thin film may be formed on a lens for scratch resistance or on a metal for corrosion protection.
It is difficult to form a thin film of amphiphilic molecules directly on a lens, so a silicon dioxide layer is initially formed on the lens in an anhydrous environment in a first chamber. The silica coated lens is then transferred to a second chamber for deposition of the film of amphiphilic molecules. During the transfer, the silica coated lens is exposed to water vapor in the air which hydrolyzes the surface and permits subsequent strong adhesion between the amphiphilic molecules and the lens. Forming the amphiphilic thin film in the same chamber as the silica layer leads to corrosion of the interior of the chamber, the contamination of the chamber preventing repeated use of the chamber for the two step process without thorough cleaning, and the undesirable formation of a messy, difficult to clean film on the interior of the chamber. Nevertheless, in some instances, the requirement of two chambers can be cumbersome.
When forming a thin film on a substrate, a film forming material is typically dissolved in a solvent. The solvent/film forming material mixture is then contacted with the substrate. One problem with forming a thin film in this manner is that the solvent is typically toxic, and may be hazardous due to flammability. In other words, the use of solvents that can dissolve film forming materials may undesirably raise serious health and environmental concerns. Disposal of the solvents is a serious environmental concern particularly in the case of oil base and halocarbon solvents.
Furthermore, the use of such solvents leads to the generation of hydrogen chloride gas as a by-product, which creates additional serious health hazards, unless a neutralizer trap is used and properly disposed according to EPA and OSHA regulations. Proper use and disposal is very difficult in a working environment, especially since an operator must track such use. Hence, each operator and lab may require having toxic gas monitors or employ the use of vapor masks, which are uncomfortable to operator.
One recent development in the field of thin film formation is the use of an ampuole to deliver a film forming material to a substrate. Using a vapor phase coating process, an ampuole containing a film forming material is placed in a vacuum chamber with the substrate. After a vacuum is established, the ampuole breaks releasing the film forming material which vaporizes and proceeds to form a film on the substrate. The ampuole is an easy to handle, convenient vehicle to charge the chamber with a film forming material. However, there are several concerns when using an ampuole in this manner.
First, when the ampuole breaks releasing the film forming material, broken glass may damage the substrate. Due to pressure differences between the inside of the ampuole and the vacuum chamber, the ampuole breaks with undesirably high force, projecting glass pieces throughout the chamber. A related problem is that the film forming material then undesirably forms a film over the broken glass pieces in addition to the substrate, thereby lowering the amount of film forming material destined for the substrate.
Second, when the ampuole breaks with high force, the film forming material tends to spurt out, leading to a non-uniform film on the substrate. The inability to control the release of the film forming material raises the need to inspection and often cleaning of coated substrates.